Experimental study on discharge coefficient of a cylindrical hole with gas jets in liquid crossflow

Abstract

This study investigates the discharge coefficient of a cylindrical hole with gas jets in liquid crossflow in a cavitation tunnel. Utilizing the Π theorem, the research examines the dimensionless parameters influencing the discharge coefficient. The results indicate that an increase in the Froude number notably diminishes the discharge coefficient at low-pressure ratios, primarily due to intensified crossflow shear effects, which constrain the effective flow area of the gas jet. However, as the pressure ratio increases, the gas jet velocity rises, attenuating the shear effect of the liquid crossflow and augmenting the discharge coefficient. Examining the correlation between total pressure ratio and discharge coefficient reveals that below a total pressure ratio of 1, the inhibiting effect of crossflow static pressure on the discharge coefficient is more pronounced than that of dynamic pressure. Conversely, beyond a ratio of 1, dynamic pressure imposes a more substantial inhibiting effect compared to static pressure. Additionally, the study assesses the impact of the jet Reynolds number on the discharge coefficient, demonstrating that the viscosity of gas jet has a negligible effect compared to the shear effect of the liquid crossflow. Furthermore, it is found that with an increase in the Euler number, the discharge coefficient increases at the same pressure or velocity ratio, decreases at the same momentum ratio, and remains unchanged at the same momentum flux ratio. Comparing the effects of those above non-dimensional parameters on the discharge coefficient indicates that the momentum flux ratio is the most significant dimensionless parameter that affects the discharge coefficient.